1. Field of the Invention
The present invention relates to a mechanism for cleaning recording and reproducing heads mounted for movement along a circular path on a rotary drum in a recording and reproducing apparatus such as a video tape recorder, a digital audio tape recorder, or the like.
2. Description of the Prior Art
Video tape recorders and digital audio tape recorders with rotary heads have rotary head drum assemblies equipped with rotary magnetic recording and reproducing heads movable along an outer circumferential surface of the rotary head drum assembly.
The rotary head drum assembly comprises a stationary drum fixed to the chassis of the recorder and a rotatable drum rotatably supported on the stationary drum. The rotary magnetic recording and reproducing heads are supported on respective supports that are mounted on the rotatable drum. The magnetic heads are positioned relatively to the stationary and rotatable drums such that their respective tape contact surfaces for sliding contact with a magnetic tape are located between the stationary and rotatable drums at the outer circumferential surface of the rotary head drum assembly.
The magnetic tape is wrapped around the outer circumferential surface of the rotary head drum assembly through a given wrapping angle. Desired signals are recorded on and reproduced from the magnetic tape by the magnetic heads which scan the recording surface of the magnetic tape while the magnetic tape is being transported and the rotatable drum is being rotated.
The signals are recorded on and reproduced from the magnetic tape at a very high density, and the magnetic heads have very small head gaps or clearances. If dust particles such as of the magnetic powder of the magnetic tape are attached to the tape contact surfaces of the magnetic heads or enter the head gaps thereof, then the signals may not be recorded on and reproduced from the magnetic tape.
To avoid such a difficulty, some video tape recorders and digital audio tape recorders have a head cleaning mechanism for cleaning the tape contact surfaces of rotary magnetic recording and reproducing heads.
One conventional head cleaning mechanism comprises a rotatable cleaning roller movable into and out of contact with the outer circumferential surface of a rotary head drum assembly, the rotatable cleaning roller being made of an elastically deformable material. When the rotatable cleaning roller is brought into contact with the rotary head drum assembly, it cleans the tape contact surfaces of the magnetic heads and also a certain area of the outer circumferential surface of the rotary head drum assembly, which area has a certain vertical width including the circular path along which the magnetic heads are rotatable.
FIG. 1 of the accompanying drawings shows such a conventional head cleaning mechanism a.
As shown in FIG. 1, a rotary head drum assembly b comprises a stationary drum c and a rotatable drum d rotatably positioned coaxially adjacent to the stationary drum c. A plurality of magnetic heads e are supported on the rotatable drum d and positioned in a small gap f defined axially between the stationary and rotatable drums c, d. The magnetic heads e are placed in respective recesses h that are defined in a lower surface of a circumferential wall g of the rotatable drum d at circumferentially spaced intervals. The magnetic heads e have respective tape contact surfaces i slightly projecting outwardly from an outer circumferential surface j of the rotary head drum assembly b.
The head cleaning mechanism comprises a vertical roller support shaft k supported on a movable member (not shown) and a cleaning roller 1 of polyurethane or the like which is rotatably supported on the upper end of the roller support shaft k. The cleaning roller 1 is horizontally aligned with an area m of the outer circumferential surface j of the rotary head drum assembly b, the area m having a certain vertical width including the circular path along which the magnetic heads e are rotatable. The cleaning roller 1 is movable by the movable member between a standby position, indicated by the solid lines, spaced from the head drum assembly b and a contact position, indicated by the two-dot-and-dash lines, held in contact with the head drum assembly b. When in the contact position, the cleaning roller 1 is resiliently held against the outer circumferential surface j of the rotary head drum assembly b.
To clean the magnetic heads e, the rotatable drum d with the magnetic heads e is rotated, and then the cleaning roller 1 is brought into the contact position. When the cleaning roller 1 contacts the outer circumferential surface j of the rotary head drum assembly b, the peripheral speed of the cleaning roller 1 initially differs from the peripheral speed of the rotary head drum assembly b. Therefore, the cleaning roller 1 rubs against an outer circumferential surface n of the rotatable drum d and the tape contact surfaces i of the magnetic heads e, thereby cleaning a portion of the outer circumferential surface n and the tape contact surfaces i.
The cleaning roller 1 can thus prevent magnetic powder particles of the magnetic tape and other dust particles from being attached to the outer circumferential surface n and the tape contact surfaces i. However, the cleaning roller 1 fails to remove deposited magnetic powder particles and other dust particles that have clogged head gaps or clearances around the tape contact surfaces i of the magnetic heads e. Heretofore, removal of such clogging dust particles has required a dedicated cleaning tape cassette to be used with the rotary head assembly a.